3.3 Given a scenario, select & install storage devices Flashcards
What does it mean that storage devices are non-volatile?
It holds data even when the system is powered off
These devices, also called mass storage, use magnetic, optical, or solid-state tech for data storage.
3 widths storage devices are produced in?
- 5.25”
- 3.5”
- 2.5”
Bays with a 5.25” width include removable panels for devices like DVD drives and smart card readers.
How is a fixed disk typically installed to a drive bay?
(storage device)
Using a caddy
(Drive is screwed into caddy, & the caddy is screwed into the drive bay)
A caddy enables fitting drives of different sizes into bays, like a 2.5” drive in a 3.5” bay or a 3.5” drive in a 5.25” bay, using an adapter. Some caddies feature rails for easy drive removal without case opening
How do external hard drives typically connect to a computer?
via USB or Thunderbolt
3 factors that impact the choice of mass storage devices?
- Reliability
- Performance
- Use
Meaning of SSD?
Solid-State Drive
How does an SSD work?
Uses flash memory for persistent storage
Flash memory outperforms mechanical HDDs, especially in read performance, with lower risks of total failure from mechanical shock and wear. Costs per gigabyte have significantly decreased in recent years
When may an SSD perform worse than an HDD?
Long, large sequential writes
SSDs can experience reduced performance due to write amplification and wear-leveling mechanisms.
What are flash chips susceptible to?
This is in relation to SSDs
Degradation over many write operations
The drive firmware and OS employ wear-leveling routines to evenly distribute writes across all SSD blocks, optimizing device lifespan
2 SSD form factors?
- M.2
- mSATA
Identify SSD form factor
M.2
Identify SSD form factor
mSATA
3 SSD communication interfaces?
- NVMe
- SATA
- PCIe
Meaning of NVMe?
Non-Volatile Memory Express
Meaning of PCIe?
Peripheral Component Interconnect Express
Main drawback to SATA/mSATA SSDs?
The 600MBps interface bottleneck
It’s a bottleneck for the best performing SSDs
The best performing SSDs can achieve transfer rates of up to 6.7 GB/s
What does the 2280 mean in 2280 M.2 SSD
The width & length of the M.2 adapter
(22mm wide & 80mm long, in this example)
M.2 adapters can be different widths & lengths
What is a HDD’s spinning disk’s speed measured in?
Revolutions Per Minute (RPM)
2 RPMs that high performance HDDs are rated at?
RPM = Revolutions Per Minute
- 15,000
- 10,000
2 RPMs that average performans HDDs are rated at?
RPM = Revolutions Per Minute
- 7,200
- 5,400
What is a HDD’s access/seek time?
Delay for the head to locate a track
What is the access/seek time of a high-performance HDD?
Under 3ms
What is the access/seek time of an average-performance HDD?
6ms
(Around 6ms)
What is a HDD’s internal transfer rate?
The speed of read/write operations on platters
What is the internal transfer rate of a 15K HDD?
(A 15,000 RPM HDD)
Up to 180 MBps
What is the internal transfer rate of a 7.2K HDD?
(A 7,200 RPM HDD)
Up to 110 MBps
What interface do most HDDs use?
SATA
What interfaces do legacy HDDs use?
PATA or SCSI
2 HDD form factors?
- 2.5”
- 3.5”
What heights do 2.5” HDDs vary in?
- 5mm
- 7mm
- 9.5mm
- 15mm
Meaning of RAID?
Redundant Array of Independent/Inexpensive Disks/Devices
What is the tradeoff with using RAID?
Sacrifices disk capacity but provices fault tolerance
How does a RAID array appear to an OS?
As a single storage resource/volume
It can be partitioned & formatted like any other drive
What is a RAID level?
i.e. RAID 0, 1, 5, 10 (1+0), etc.
Drive configuration with specific fault tolerance
Basic RAID levels are numbered from 0-6. There are also nested RAID solutions, like RAID 10 (RAID 1 + RAID 0)
3 ways RAID can be implemented?
- Software RAID (OS features)
- Hardware RAID (Adapter Card)
- Integrated RAID (Integrated on the MOBO)
Hardware RAID options vary from basic support for RAID 0 or RAID 1 to more advanced levels like RAID 5 and RAID 10. They often enable hot-swapping of damaged disks without system shutdown.
What characteristic should all disks in an RAID array share?
Failure to have the same characteristics may result in suboptimal performance, compatibility issues, and potentially data loss
Capacity, type, & performance
What happens if there are different disk sizes in a RAID array?
The smallest disk limits usable space
What is disk striping in RAID?
Dividing data into blocks across all drives
This improves performance as multiple disks are available to service requests in parallel
How many disks does RAID 0 require?
At least 2
What does RAID 0 do?
Stripes data across multiple drives without redundancy
RAID 0 only has specialist uses–typically as some type of non-critical cache store
What does it mean that RAID 0 provides no redundancy?
If any disk fails, the whole logical volume will fail
This will cause the computer to crash & requires data to be recovered from backup
What does RAID 1 do?
Mirrors data across multiple drives for redundancy
Each write operation is duplicated on the second disk on the set. If one disk fails, the other takes over.
How many disks does RAID 1 require?
Atleast 2
What is RAID 1’s disk utilization?
50%
i.e. if you have two 1TB drives in a RAID 1 configuration, the total usable capacity is 1TB because the second drive mirrors the data from the first drive, effectively halving the usable space
What does RAID 5 do?
Stripes data & parity data
What is parity data?
Calculated value for error detection & fault tolerance in RAID
It’s generated from the data stored on the array
What is parity data used for?
Reconstructing data after a drive failure
When is the read/write operation performance degraded in RAID 5?
When a disk fails
due to the need to recover the data using the parity data
How many disks does RAID 5 require?
Atleast 3 disks
The controller or OS sets a maximum number of devices, but practical factors such as cost and risk often determine the actual number of drives used
When does the whole logical volume fail in RAID 5?
Meaning, in what situation does the whole volume become unavailable
When more than one drive fails
This means that adding more disks increases the chance of failure
How much data is reserved for parity in RAID 5?
A fraction of each disk’s capacity
The fraction is determined by the number of disks used in the array
i.e. if 3 disks are used, a third of each disk is set aside for parity. If 4 disks are used, a quarter is used for parity. i.e. in a 3 80GB disk configruation (240GB total), a third of each disk (26.4GB (a total of 80GB (3 * 26.4 = 80))) is used for parity, giving a usable volue of 160GB (240 - 80 = 160)
What does RAID 10 (RAID 1 + RAID 0) do?
Mirrors data across striped drive pairs
How does RAID 10 (RAID 1 + RAID 0) offer excellect fault tolerance?
One disk in each mirror can fail without losing data
How many disks does RAID 10 (RAID 1 + RAID 0) require?
Atleast 4 disks, & an even number of disks
What is RAID 10’s disk utilization?
50%
This means that half of the total disk capacity is utilized for redundancy (mirroring). i.e. if you had 4 1TB drives, the usable storage capacity is 2TB due to the mirroring configuration, resulting in 50% disk overhead
Meaning of NAS?
Network Attached Storage
What is a NAS device?
Drive enclosure that connects directly to the network
Rather than to a PC
Advanced enclosures can host multiple disk units configured as a RAID array
What is the max capacity of original SD cards?
2GB
What is the max capacity of SDHC cards?
A type of SD card
32GB
What is the max capacity of SDXC cards?
2TB
How do smaller SD cards fit into regular-size readers?
i.e. microSD, microSDHC, microSDXC
Using a caddy
Meaning of CD?
Compact Disc
Meaning of DVD?
Digital Versatile Discs
Meaning of BD?
(optical drive)
Blu-ray Discs
How is data on optical media read?
via laser
Optical discs are marketed as being hard-wearing, but scratches can render them unreadable
Can optical disks be used as storage media for PC data?
Yes
What does it mean if an optical drive is formatted as basic recordable media?
Can be written once only in a single session
What does it mean if an optical drive is formatted as multisession recordable media?
Writable in multiple sessions, but data is not erasable
What does it mean if an optical drive is formatted as rewritable media?
Writable & erasable over multiple sessions, with limited write cycles
What formats are CDs available in?
- Recordable (CD-R)
- Rewritable (CD-RW)
What is the capacity of DVDs?
- 4.7GB (Single-layer, single-sided)
- 17GB (Dual-layer, double-sided)
What formats are modern DVD drives compatible with?
- DVD+R/RW
- DVD-R/RW
At launch, there were competing DVD+R/RW & DVD-R/RW recordable & rewritable formats, but most drives can use either, designated by the “±” symbol
What is the capacity of Blue-ray discs?
25GB per layer
How are internal optical drives installed?
Via 5.25” drive bay
How are internal optical drives connected to the MOBO?
via SATA data & power connectors
How are external optical drives connecting to the PC?
via USB
(or possible eSATA or Thunderbolt)
External optical drives usually come with their own AC adapter for power. They may feature either a tray-based or slot-loading mechanism
